1. Field of the Invention
The present invention relates to a manufacturing equipment of a liquid crystal display (LCD) device, and more particularly, to an apparatus for automatically setting an over-driving look-up table to be stored in a memory device included in an LCD device, and a control method thereof.
2. Discussion of the Related Art
A typical LCD device controls light transmittance of liquid crystal (LC) in response to video data to display an image corresponding to the video data. LCD devices may form display screens of nearly unlimited size. In addition, LCD devices may be manufactured with slim profiles and light weights. Accordingly, LCD devices may be used as a display device for computers and television receivers as a substitute for cathode ray tube (CRT) display devices.
An LCD device applies pixel driving signals (or voltages) corresponding to a gray scale to LC cells arranged in a matrix configuration. LC molecules included in each LC cell are aligned in a direction corresponding to a potential difference between a pixel driving signal and a reference voltage (or common voltage). An amount of light passing through the LC cell varies according to the alignment directions of LC molecules allowing an image to be displayed.
Depending on the particular physical operation mode (for example, the direction of rotating motion) of LC molecules in an LCD device, the response time, which is a period of time for forming an image upon application of corresponding video data, may be relatively slow. As a result, a motion blurring phenomenon where the outline of an object is blurred and a ghost phenomenon are generated in moving images displayed by an LCD device.
To prevent generation of the motion blurring phenomenon and the ghost phenomenon, an over-driving algorithm is applied in driving the LCD device with video data. The over-driving algorithm uses an transient pixel driving signal with a gray scale having a greater difference than a difference between a previously supplied gray scale and a currently supplied gray scale to be applied to an LC cell for a predetermined time (i.e., one frame period) when an image changes (i.e., the gray scale of a pixel to be displayed by the LC cell changes between frames). The speed of physical operation of LC molecules contained in an LC cell is increased by using the transient pixel driving signal having a greater gray scale than the gray scale of the originally supplied pixel data, thus improving the response time of an LCD device. In addition, to allow an LCD device to have a constant response time regardless of the frame to frame differences in gray scale for a pixel, a difference between a gray scale that and a gray scale of a transient pixel driving signal may be increased as the frame to frame difference in gray scales changes.
As one alternative for implementing an over-driving circuit construction, an LCD device uses an over-driving look-up table in which transient pixel driving data having various gray scale differences for a pixel depending on the frame to frame variation in pixel gray scale. The gray scales of transient pixel data contained in the over-driving look-up table are modified depending on the physical property of the liquid crystal, the design specification of an LCD device, and the particular model for the LCD device.
To prepare the over-driving look-up table, video data of an initial gray scale, transient video data, and video data of measurement object gray scale are sequentially displayed on an LCD device. Simultaneously, an operator checks light change of an LCD device using by a measuring device to determine appropriate transient pixel data. The operator repeatedly performs the above-described image displaying operation while changing the gray scale of the transient video data several times with respect to an arbitrary gray scale. Transient pixel data are prepared for each gray scale by repeatedly performing the above-described a transient pixel data setting operation for each gray scale. Finally, the transient pixel data for each gray scale are mapped and stored in the form of an over-driving look-up table by an operator.
In the above described method, populating the over-driving look-up table of an LCD device depends on input of video data through an operator's manual operation and measurement of light change on an LC display panel. Setting the values for the over-driving look-up table requires a long period of time using the described manual method. In addition, the accuracy of transient pixel data is inevitably reduced due to an operator's inaccuracies in measuring a change in the light waveform detected using the measuring device, and there may be deviations in measurements obtained by different operators. In addition, the process of making or setting the over-driving look-up table for each LCD device is difficult.